From
Human Destiny, a work by the French scientist Lecomte du
Nouy, published in 1947 by Longmans, Green & Co. (emphasis in
original):

"Certain
of our mental illusions are due to the fact that we consider a phenomenon,
as we observe it, in the frame of our current life. Motion in a straight
line, for instance, is real with respect to the earth, and false with
respect to the universe. This does not only apply to sensory illusions. It
applies to all our human observations which are always relative to the system
of reference chosen. By system of reference we simply mean the scale
of observation. This demands an explanation.

"Let
us suppose that we have at our disposal two powders. One white (flour) and
the other black (finely crushed charcoal or soot). If we mix them we will
obtain a gray powder which will be lighter in color if it contains more
flour and darker if it contains more soot. If the mixture is perfect, on
our scale of observation (that is, without the help of a microscope)
the phenomenon studied will always be a gray powder. But let us suppose
that an insect of the size of the grains of flour or of soot moves around
in this powder. For him there will be no gray powder, but only black or
white boulders. On his scale of observation the phenomenon, 'gray powder,'
does not exist.

"The
same is true of any print or engraving. When examined with a magnifying
glass, the nose of George Washington will look to us like a succession of
black and white points. Under the microscope, we will see nothing but the
grain of the paper, gray, black, or white according to whether it has been
covered by ink or not. The principal phenomenon, the design, the portrait
of Washington, has disappeared. It only existed on our normal scale of
observation.

"In
other words, one can say that from the standpoint of man it is the
scale of observation which creates the phenomenon. Every time we
change the scale of observation we encounter new phenomena.

"On
our scale of human observation, as pointed out before, the edge of a razor
blade is a continuous line. On the microscopic scale, it is a broken but
solid line. On the chemical scale we have atoms of iron and carbon. On the
sub-atomic scale we have electrons in perpetual motion which travel at the
rate of several thousand miles per second. All these phenomena are in
reality the manifestations of the same basic phenomenon, the motions of
the electrons. The only difference which exists between them is the scale
of observation.

"This
fundamental fact was first pointed out by a brilliant Swiss physicist who
died in 1942, Professor Charles-Eugene Guye. It enables one to understand
many things and to avoid grave philosophical errors."